Polymer-particle interface

Adsorption diaiacteristics of Surfactants on Water-Monomer and Aqueous Phase-Polymer Particle Interfaces... 

Bansal A, Yang H, Li C, Benicewicz BC, Kumar SK, Schadler LS (2006) Controlling the thermomechanical properties of polymer nanocomposites by tailoring the polymer-particle interface. J Polym Sci B Polym Phys 44(20) 2944—2950... 

Without additional surfactant, the emulsion could not be stabilized solely be the ricinoleic acid and phase separation occurred. The coalesced monomer phase was loaded with magnetite particles, showing that the phase transfer of magnetite was successful (see Fig. 18). With additional surfactant, a stable miniemulsion resulted. TEM images of the composite parties after polymerization however revealed that the magnetite particles were located at the polymer particle interface and inhomogeneously distributed (see Fig. 18). Presumably pickering emulsions... 

Solomatov et al. [131] derived an equation for strength at the polymer - spherical particle interface ... 

Yin et al. [73,74] prepared new microgel star amphiphiles and stndied the compression behavior at the air-water interface. Particles were prepared in a two-step process. First, the gel core was synthesized by copolymerization of styrene and divinylbenzene in diox-ane using benzoylperoxide as initiator. Microgel particles 20 run in diameter were obtained. Second, the gel core was grafted with acrylic or methacryUc acid by free radical polymerization, resulting in amphiphilic polymer particles. These particles were spread from a dimethylformamide/chloroform (1 4) solution at the air-water interface. tt-A cnrves indicated low compressibility above lOmNm and collapse pressnres larger than 40 mNm With increase of the hydrophilic component, the molecnlar area of the polymer and the collapse pressure increased. 

Wet out solid substrates. Act as a functional additive at the polymer/air interface, e.g. filler particle surfaces, and help their uniform dispersion in a polymer matrix without agglomeration. 

Taniguchi T, Takeuchi N, Kobaru S, Nakahira T (2008) Preparation of highly monodisperse fluorescent polymer particles by miniemulsion polymerization of styrene with a polymerizable surfactant. J Colloid Interface Sci 327 58-62... 

Polymers interpenetration of polymer chains, phase separation, compatibility between polymers, interdiffusion of latex particles, interface thickness in blends of polymers, light-harvesting polymers, etc. 

This raises the question of whether diffusion plays a role in the kinetics of slurry polymerization. Certainly there is no limitation across the gas-liquid interface doubling the catalyst also doubles the polymer yield, but increasing the stirring rate does nothing. Diffusion through the polymer particle is a more troubling issue. There are times when the polymerization clearly becomes diffusion limited, or fouled, due to solvation of the polymer, but this is rarely a problem if the temperature is kept down and the molecular weight up. 

It is accepted that the radical entry rate coefficient for miniemulsion droplets is substantially lower than for the monomer-swollen particles. This is attributed to a barrier to radical entry into monomer droplets which exists because of the formation of an interface complex of the emulsifier/coemulsifier at the surface of the monomer droplets [24]. The increased radical capture efficiency of particles over monomer droplets is attributed to weakening or elimination of the barrier to radical entry or to monomer diffusion by the presence of polymer. The polymer modifies the particle interface and influences the solubility of emulsifier and coemulsifier in the monomer/polymer phase and the close packing of emulsifier and co emulsifier at the particle surface. Under such conditions the residence time of entered radical increases as well as its propagation efficiency with monomer prior to exit. This increases the rate entry of radicals into particles. 

Guo et al. [29] have estimated the entry rate coefficient, k a, of radicals into micelles (microemulsion droplets) to be 7xl05 cm3 mol-1 s 1, which is several orders of magnitude smaller than ka, the entry rate coefficient into the polymer particles. This was ascribed to the difference of the surface area of microemulsion droplets and polymer particles. The condensed interface layer or the possibly high zeta-potential of the surface of the microemulsion droplets may hinder the entry of radicals. 

The ratio Mw/Mn (MWD) decreased with increasing PEO-MA fraction in the monomer feed and/or the number of EO units in the macromonomer. Generally, the Mw/Mn in bulk (homogeneous) systems is a function of the termination mode and the chain transfer events and varies between 1 and 2. In the present disperse systems, MWD is much broader (much above 2) as a result of further contributions, such as polymerization in the continuous phase, interface, and polymer particles. The chain transfer to PEO chains decreased the molecular weight, i,e., the Mw of copolymer decreased with increasing macromonomer concentration and PEO chain length. 

We also note that carboxylate ions which are chemically combined at the polymer-water Interface are known to be considerably more effective in conferring mechanical stability upon a latex than are carboxylate ions which are held at the interface by adsorption. Presumably this is because the latter are able to move laterally in the particle surface, whereas the former are not.) We propose that a given number of adsorbed soap anions is more effective in conferring mechanical stability if able to move independently of... 

It is seen that the adsorption of Igepal CO-630 at the three latex/water interfaces decreases with increase in polarity of the vinyl acrylic latex surface. Explanation for such a decrease in surfactant adsorption at a polymer/water interface with increase in polymer polarity has been discussed in detail elsewhere (1). Briefly, increased polarity of the polymer lowers the interfacial free energy of the polymer latex/water interface and this, in turn, reduces the free energy of adsorption for a simple saturation type adsorption process of a surfactant at a latex surface in aqueous media. Such a lowering in free energy of surfactant adsorption at a polymer latex/water interface with increase in polymer polarity leads to the observed results, namely, decrease in the adsorption of Igepal CO-630 with polarity increase of the VA/BA latex particle. 

E. Wolert, S. M. Setz, R. S. Underhill, R. S. Duran, M. Schappacher, A. Deffieux, M. Holderle, and R. Mulhaupt, Meso- and microscopic behaviour of spherical polymer particles assembling at the air-water interface, Langmuir 17, 5671-5677 (2001). 

Free-Radical Polymerization in Emulsion. In suspension polymerization, the particle size is fixed by the size of the monomer droplet which contains the initiator. Emulsion polymerization differs from suspension polymerization in that the initiator is dissolved in the aqueous phase and the polymer particle grows during polymerization. Free radicals are generated in the water and diffuse to the monomer-water interface. The length of the polymer chain formed, or equivalently the molecular weight, depends on the rate of free radical arrival and termination. S. Katz,... 

It should be noted that because of the insolubility of the polymer, there is no change in monomer concentration at the particle interface in... 

For a successful incorporation of a pigment into the latex particles, both type and amount of surfactant systems have to be adjusted to yield monomer particles, which have the appropriate size and chemistry to incorporate the pigment by its lateral dimension and surface chemistry. For the preparation of the miniemulsions, two steps have to be controlled (see Fig. 14). First, the already hydrophobic or hydrophobized particulate pigment with a size up to 100 nm has to be dispersed in the monomer phase. Hydrophilic pigments require a hydro-phobic surface to be dispersed into the hydrophobic monomer phase, which is usually promoted by a surfactant system 1 with low HLB value. Then, this common mixture is miniemulsified in the water phase employing a surfactant system 2 with high HLB, which has a higher tendency to stabilize the monomer (polymer)/water interface. 

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